The following terminology is used in this text. The expression “kinematic state of a physical component” refers to the position, and/or velocity, and/or acceleration of the physical component with respect to some pre-determined reference system. The expression “relative kinematic state of two physical components” refers to the position, and/or velocity and/or acceleration of the physical components relative to each other. The expression “kinematic quantity” is used in this text to refer to a physical quantity representative of the kinematic state.
The relative kinematic state of two physical components can be measured using any of a variety of sensing techniques. An example of a known sensing technique is based on determining the strength of a magnetic field, or a rate of change in the magnetic field strength, as a representative of relative position or of relative velocity of a first physical component relative to a second physical component. Magnetic sensing is an example of a remote sensing technique. That is, it is contactless in that a magnetic sensor arrangement does not introduce any physical contact with the first and second components. As a result, a magnetic sensor arrangement is practically insusceptible to, e.g., the accumulation of dirt on the components, to the presence of lubricants and, if properly designed, to magnetic fields from an external source.
U.S. Pat. No. 6,051,969 discloses a sensor rotor for detecting wheel speed. The sensor rotor comprises a magnetized ring. The magnetized ring comprises a plurality of ring pieces having outer and inner edges that are identical in radius of curvature to each other. The ring pieces are arranged in the shape of a ring. The magnetized ring is made by magnetizing in such a manner that opposite magnetic poles are formed alternately in the circumferential direction thereof. The sensor rotor also has a press-in ring to the inside of which the magnetized ring is fixed.